The corrosion resistance of several commercial alloys was investigated in laboratory retort tests under a reducing sulfidizing mixed gas at 700 and 900°F (371 and 482°C) for 1000 hours. The test conditions were designed to simulate the corrosion of furnace walls in the combustion zone of utility boilers burning sulfur/chlorine-bearing coal substoichiometrically. Corrosion rates of these alloys were determined and compared to those obtained from a previous study in which the same alloys were evaluated under chlorine-free substoichiometric combustion environments. Results of the two studies reveal that the presence of chlorine in the reducing/sulfidizing mixed gas has a negligible effect on the corrosion behavior of these alloys in this gas at 700°F (371°C), whereas a beneficial effect was observed at 900°F (482°). The beneficial effect implies that the presence of HC1 may impede the sulfidation attack by H2S under certain substoichiometric combustion environments.
Keywords: Corrosion, Chlorine, Substoichiometric Combustion, Sulfidation, H2S, Mixed gas.